In-season testing is banned in Formula 1, but both Mercedes and Pirelli believe the running was permitted within the regulations.

Red Bull, Ferrari, Mercedes and Pirelli were all been summoned to see the stewards after the race.

The official notice from the FIA read: "Protests have been lodged by Infiniti Red Bull Racing and Scuderia Ferrari concerning an alleged breach of Article 22.4 h) of the FIA Formula 1 Sporting Regulations.

"Both teams alleged the Mercedes AMG Petronas F1 Team have conducted three days of track testing using a 2013 car on the 15th, 16th, 17th of May in Barcelona, i.e. between the period that the precedes the start of the first Event of the championship and 31 December of the same year."

The crux of the matter appears to be the use of Mercedes' W04 car in the test.

Speaking to Sky Sports F1's Ted Kravitz after seeing the stewards, Mercedes Team Principal Ross Brawn explained that the test came at Pirelli's request.

The Italian manufacturer is introducing modified tyres in Canada on safety grounds after the delaminations which occurred in Bahrain and Spain. Furthermore, they are also working on next year's specification.

"We obviously explained to them the circumstances behind what happened; I'm reasonably comfortable with what we did," Brawn said.

"We did it at the request of Pirelli. There was a serious issue with the tyres which we've all experienced and that needed fixing as soon as possible.

"We've explained to the stewards what was done and it's now up to them. We're comfortable with the position we're in.

"One point I want to allay is this concept of a 'secret' test. There's never a secret in Formula 1. The test was starting when lots of teams were still in Barcelona packing up, so if we'd wanted a secret test we'd have gone off somewhere where no-one could find us.

"It's a bit of innuendo that's unfortunate.

"We don't know what we were testing. When they present the test programme, all the tyres are anonymous."

Brawn also said that Red Bull and Ferrari had opportunities to conduct additional testing.

"I know why they feel aggrieved by it but it was a Pirelli tyre test, it wasn't a Mercedes test. That's an important thing to understand," he added.

"There's a provision in the contract between Pirelli and the FIA to allow every team to do 1,000km of testing at Pirelli's request.

"Pirelli have requested that in the past and nobody has supported them. So if those teams are aggrieved then perhaps they should look at that aspect."